Abstract:

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The use of natural gas as an alternative fuels are motivated from the impact in deteriorating quality of air and the energy shortage from petroleum products. Through retrofitting, CI engine runs on CNG, will be able to reduce the negative impact mainly on the use of petroleum products. However, this required the modification of the combustion chamber geometry by reducing the compression ratio to value that suits combustion of CNG. In this present studies, four different shapes and geometries of combustion chamber were designed and simulate using CFD package powered by Ansys workbench, where k-ε turbulence model was used to predict the flow in the combustion chamber. The results of turbulence kinetic energy, velocity vectors and streamline are presented. The enhancement of air-fuel mixing inside the engine cylinder can be observed, where the design with re-entrance and lower center projection provide better results compared to other combustion geometries designs.

Abstract: In order to promote the quality of mixture and improve the fuel spray spatial distribution, enhancing airflow movement in a combustion chamber, a new swirl chamber combustion system in DI (direct injection) diesel engines is proposed based on conical-spray. Numerical simulations have been conducted by using the FIRE v2008 code. Several different widths of passage and spray angles are investigated in a single cylinder 135 diesel engine. The combustion and emissions performance were investigated by different conical-spray nozzles and combustion chambers with a constant compression ratio. The results show that using this combustion system, the mixture formation and combustion processes have been improved by a certain longitudinal swirl when the air is squished into the swirl chamber through the relative narrow passage. Moreover, the formation of homogeneous mixture is accelerated and the combustion is improved compared with that of conventional combustion system. The cases show the passage width of 5mm and conical spray cone angle of 140° has a better performance in the new combustion system.